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Complex Source Behaviors and Spatiotemporal Evolution of Seismicity During the 2015–2016 Earthquake Sequence in Cushing, Oklahoma
Author(s) -
Meng Qingjun,
Ni Sidao,
Peng Zhigang
Publication year - 2021
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2021jb022168
Subject(s) - seismology , induced seismicity , geology , foreshock , sequence (biology) , slip (aerodynamics) , fault (geology) , shear (geology) , aftershock , intraplate earthquake , tectonics , paleontology , genetics , physics , biology , thermodynamics
In September and October 2015, three M 4+ earthquakes occurred as a sequence along a fault northwest of the Cushing city, Oklahoma, followed by another M 5 earthquake in November 2016. While previous studies have shown that moderate‐size earthquakes in Oklahoma are likely induced by wastewater injections, it is still not clear what controls the rupture process and spatiotemporal evolutions of seismicity during individual sequences. In this study, we investigated the rupture process of these four M 4‐5 events in 2015–2016 with finite fault model (FFM) inversions, and computed the static stress changes during this sequence. We found that the rupture processes of four M 4‐5 earthquakes were very complex, and each of them had several subevents with different rupture directivities. The 2016 M 5 earthquake started near the region where three M 4+ events initiated, but the majority of the slip occurred a few kilometers away in the northeast direction. In comparison, the 2015 M 4.3 event mainly ruptured toward the southwest direction. Due to data limitation and inversion uncertainties, we were unable to constrain the rupture directivities for the other two M 4+ events. The foreshocks 3 days before the first M 4+ earthquake in 2015 occurred in a region of positive shear stress changes caused by previous earthquakes in 2014–2015 on unmapped faults several kilometers to the south. Our results suggest small‐scale heterogeneity in controlling complex seismicity and rupture patterns in the 2015–2016 Cushing sequence, and possible triggering of this sequence by a small stress perturbation on order of a few kilopascals.